Step 1: Preheat your oven to 350°F (175°C).
Step 2: Line a 9x13 inch baking pan with parchment paper and lightly grease it.
Step 3: In a large mixing bowl, whisk together 2 cups of sugar and ¾ cup of cocoa powder. Add 1 cup of melted butter, 4 eggs, and 2 teaspoons of vanilla extract; mix until smooth. Gradually fold in 1½ cups of flour and ½ teaspoon of salt until combined.
Step 4: In another bowl, cream together 1 cup of softened butter, 1 cup of sugar, and 1 cup of brown sugar until light and fluffy. Add 2 eggs and 2 teaspoons of vanilla; mix well. In a separate bowl, combine 2½ cups of flour, 1 teaspoon of baking soda, and a pinch of salt. Gradually add to the wet mixture, stirring until just combined. Fold in 1 cup of chocolate chips.
Step 5: Pour the brownie batter into the prepared baking pan. Dollop spoonfuls of cookie dough on top and spread it out to cover.
Step 6: Bake for 30-35 minutes, or until a toothpick inserted comes out with moist crumbs.
Step 7: Allow to cool for 15 minutes in the pan, then lift out using the parchment paper and cool completely on a wire rack before cutting into squares.